部落格

I have described you how to use Openlayers as map brower, but Openlayers is more than a map viewer. In this part, you will know some advanced usage for Openlayers.

GetFeatureInfo

GetFeatureInfo request is one quest of WMS, it will tell you what is the attribute of one geometry, which you have clicked to view it's detail on the map. The result of attribute has two forms, one is xml and the other is html. Because our browser will filter the xml tag, we should use html format unless you have your own program to parse the xml request. This is one GetFeatureInfo request URL:

Openlyaers allow you combining several Map servers in onemap viewer.
In part I, I have introduced how to use Google, Yahoo,or Virtual Earth map. If you are the fans of them all, you will never miss such appilcation.

Part I tells you one easy way to put GoogleMap, VE or other Mapservers in your blog or site, that is not enough for our Gisers. If you have built your own map server by using UMN MapServer or SUAS MapServeri, or you have collected some useful WMS servers, Openlayers can help you create map viewer client (please download Openlayers toolkit firstly).

One OGC standard WMS should have these parameters:VERSION=1.1.1REQUEST=GetMapBBOX=3504755.432,5395574.262,3521889.2572,5415182.5352

There are a considerable number of WMS/WFS clients, some are open source, some are comercial softwares; some have comprehensive functions and atmpting interface, but complex to config and use, some have succinct interface and simple to control, howerver, they can support only part of functions; some you have paid for them, but they leave much to be desired, some are free, and make you satisfactory; some are programmed by traditional languages C, Vb, PHP, ASP, some are using new techniqure, Ajax, Flash.

GeaBiosstands for Geo Enabled And Better Internet Oriented Services and it comes from a group of academics from Slovenia. Combined with WebGiS, Flash, Ajax, although the usability could definately be improved, the core WMS/WFS functionality is fantastic and integration with other XML sensor feeds(Population from Eurost

The geographical information web Mapper, giMapper, has been developed as an alternative to the well established open source project MapServer. It uses Shapefiles as data source to display the map, your system requirement are only listed as below:HTML, javascript, PHP (v4.3+) and GD (v1.6+), without Database and other software. Of cource, using Shapefiles a datasource directly means the toolkit reads and parses the data at first and then draw the vector data through PHP GD function, just like UMN Mapserver has done. But this way is not efficient, unless your server side is programmed with C++. It is an embarrassed task for PHP, exactly to say.

But giMapper has its reason to do that: "We needed a way of browsing a UK map which had hot spots identifying particular places or people. The project started to use MapServer but it soon became evident that to use MapServer in the final application would require access to the server's root for installation and configuration - something we did not have." OK, the toolkit points to the users, who have not their own host server and the Server does not support Database, or installation of other software(such as UMN MapServer). I am lucky, my server support Database at least :)

The toolkit includes Server side and map browser client. You should know, giMapper is not based on OGC WMS standard, but i can publish map well.

I found one WebGIS application for china recent climate change here, http://www.webgis-china.de/, some scholars from Gutenberg University did that. The website assesses recent Climate Change in China over the past 50 years. " Well-adopted statistical methods of trend computations that are commonly applied for climatic change studies were applied for this study based on monthly temperature records over the 50 year observation period 1951 - 2000 for totally 165 main meteorological stations. The reference stations are located all over China though they are preferably distributed over the eastern part of the country."

Is there some relationship between PDF and GIS? As I thought before, it is enough to display the map using PDF. Interaction with PDF? Just like SVG, Flash, or Ajax? Interesting but impossible. But GeoPDF from Terragotech has broken the embarrass.
You need download one small plugin for Arcobat PDF reader, it is free.
The GeoPDF Toolbar allows you to view multiple coordinate display, re-project to most coordinate systems, measure distance and bearing, zoom to any coordinate, and connect to GPS and track. Here you can view some demo how to use it.